The present invention relates to an apparatus for noninvasive testing and monitoring of biological molecules such as glucose.
Diabetes mellitus is a medical condition in which the body does not adequately produce the quantity or quality of insulin needed to maintain normal levels of glucose in the circulating blood. The two most common types of diabetes are type I, also known as Insulin Dependent. Diabetes Mellitus (IDDM), which accounts for 5-10% of all cases, and type II or Non-Insulin Dependent Diabetes Mellitus (NIDDM), which accounts for 90-95% of all cases. IDDM occurs in childhood, and those suffering from the disease require insulin doses throughout their lives. NIDDM generally occurs in adults and, although insulin may be required, the disease may be controllable with oral medication, weight loss, a nutritious diet and a regular exercise program.
Diabetes affects about 16 million people in the U.S. and over 100 million people worldwide. Diabetes can lead to severe health complications associated with the accumulated affects of poor blood glucose control, including blindness, kidney failure, heart failure, and peripheral neuropathy associated with limb pain, poor circulation, gangrene and subsequent amputation (Davidson, Diabetes Mellitus—Diagnosis and Treatment, 3rd Edition, Churchill Livingstone, New York, 1991). As a result, frequent self-monitoring of blood glucose is crucial for effective treatment and for reducing diabetes-associated morbidity and mortality.
Currently glucose measurements are done by pricking a finger and extracting a drop of blood, which is applied to a test strip, causing a color reaction between blood glucose and chemicals on the test strip that can be analyzed by an optical meter (glucometer) to give a numerical glucose reading. However, the current glucose tests are painful, disrupt daily life, and may be difficult to perform in long term diabetic patients due to calluses on the fingers and poor circulation. As a result, the average diabetic patient tests his/her blood glucose levels less than twice a day, far fewer than the recommended 4-7 times a day, leading to poor blood glucose control.
A non-invasive glucose monitoring method that is fast, painless and convenient could provide adequate control and greatly reduce the complications commonly seen in diabetes patients and consequently reduce health care costs.
Several types of non-invasive glucose monitoring techniques have been proposed. These techniques measure glucose levels in blood, interstitial fluid, ocular fluids and sweat and include microdialysis, wick extraction, implanted electrochemical or competitive fluorescence sensors, extraction fluid technqiues (iontophoresis, skin suction and suction effusion techniques) and optical techniques, such as near-infrared spectroscopy, infrared spectroscopy, Raman spectroscopy, photoacoustic spectroscopy, scatter and polarization changes.
Currently, the most actively studied non-invasive methods for blood glucose measurement are optical techniques. All are limited by low signal-to-noise ratios and poor reproducibility. Current instrumentation lacks specificity due to substantial chemical and physical interference.
Several patents have discussed the use of magnetic fields for the non-invasive detection of certain substances in the human body systems. In nuclear magnetic resonance (NMR), for example, permanent magnets have been used to create a first, or biasing magnetic field to align initially randomly oriented hydrogen protons present in the nuclei of a substance in the sample being tested. A second energy field is applied to increase the energy level of the nuclei. When the second energy field is allowed to collapse, the nuclei return to their original, unaligned state, releasing energy that is detected and analyzed in the form of an image or spectrum. Such spectra are characteristic of individual substances. As a result, NMR may be used to establish the presence and identity of such substances and the concentrations in which such substances are present.
French Patent No. 2,562,785 (Jeandey et al.) discusses a permanent magnet system for NMR imaging medical diagnostics using pole pieces separated by and bridging stacked permanent magnets to form an open examination area and electromagnetic coils to adjust the resulting magnetic field.
Japanese Patent No. 56-14145 (Nippon Denshi K. K.) discusses an arrangement of permanent magnets held within a cylinder. A spacer is placed within the cylinder and sandwiched about the spacer are a pair of cylindrical pole pieces having raised central portions that extend into the air gap between the pole pieces and from which the operative flux emanates.
U.S. Pat. Nos. 4,875,486 and 5,072,732 (Rappaport et al.) describe nuclear magnetic resonance apparatus for non-invasive blood glucose testing that includes a pair of opposed biasing permanent magnets, a surface coil apparatus mounted adjacent the biasing magnets, and an electronic circuit controlled by a microprocessor. The microprocessor activates an RF generator and a cyclically-operated gate, which excites the surface coil. The surface coil applies a second magnetic field, raising the energy state of glucose molecules in a patients finger and aligning their nuclei. The microprocessor then deactivates the RF generator, permitting the nuclei (dipoles) to relax and return to their original alignment, releasing energy that is detected by the surface coil and analyzed by the microprocessor. The process is repeated with a standard sample and the test results with the patient's finger are compared with the results obtained with the standard sample to determine the glucose concentration in the patient.